Self-propelled watercraft, such as canoes and kayaks, may be manufactured in a variety of ways. For example, some plastic watercraft may be made via rotational molding. Rotational molding involves melting a plastic in a heated mold cavity, and then rotating the mold cavity while cooling the cavity to thereby coat the cavity with polymer as it cures or otherwise solidifies.
Rotational molding of a kayak allows a deck and hull of a canoe or kayak to be formed as a single unitary structure. Further, in some situations, a canoe or kayak seat may also be formed integrally with the deck and hull in a single rotational molding process. For example, in a recreational sit-in kayak (i.e. a kayak having a deck with an open cockpit in which a user sits), an integrally molded seat may extend downward from each side of the cockpit into the cockpit opening.
To provide further support for an integrally molded seat, a watercraft mold may be designed such that one or more kiss-offs are formed between a bottom surface of the seat and an interior surface of the hull during rotational molding. A kiss-off is a bridging structure formed during rotational molding at locations where two mold surfaces come in close proximity but do not contact one another. Plastic deposited on the two mold surfaces can flow together to create the kiss-off structure due to the close proximity of the mold surfaces.
Various difficulties may be encountered when forming kiss-offs in a rotationally molded watercraft. For example, a kiss-off used for structural reinforcement, such as a kiss-off extending between a seat and hull, may be difficult to form with a thick enough wall to withstand repeated stresses and/or to reproducibly meet desired manufacturing tolerances.